Ostriker & Peebles
[105]
suggested that the existence of massive halos
around spiral galaxies was needed in order for the disks
to be stable against bar formation. Their paper led
Lecar [84]
to suggest that the diffuse dark matter in
Coma comes from tidally torn-off halos. Indeed, the
lack of significant
luminosity segregation of Coma galaxies may indicate that they have lost their
massive halos very early in the history of the cluster (see
Section 6.1).

Support to his model came from the
observations of Thompson
[134], who showed
that the density of barred galaxies is higher in
the cluster centre, as predicted if these galaxies have
indeed lost their halos.

Lecar's hypothesis would imply similar
mass-to-light ratios for galaxies and clusters, and this is consistent with
current estimates (e.g. Bahcall
[11]).